Measure corticosterone secretion in adult male rats following denervation of the pineal or a sham operation. Reverse the photoperiod and check for reestablishment of the diurnal corticosterone rhythm in both groups. Compare the pattern of estrogen and progesterone secretion in adult female rats after denervation of the pineal with the pattern in sham operated controls. Follow the growth and sexual differentiation of rats raised under lights differing in wave length and intensity.